1. Field of the Invention
This invention relates to an editing system and method and a distribution medium and more particularly to an editing system and method and a distribution medium which are capable of quick editing.
2. Description of the Related Art
In recent years, various computer systems have been developed rapidly, consumers have become eager to require enhanced external memory with the development of computer systems. The device that had developed in response to the request is a disk array unit. A disk array unit has a plurality of built-in disk devices therein to enlarge the capacity, in which disk array unit disk devices are operated in parallel to speed up reading operation and writing operation and error correction data is involved to improve the reliability.
When the data is stored in a disk array unit, the data is divided into a plurality of subblocks, error correction data is generated for each subblock, all the subblocks and error correction data are written in separate disk devices respectively.
On the other hand, when the data is read out from a disk array unit, a plurality of subblocks and error correction data are read out simultaneously from disk devices in which subblocks and error correction data, components of the data, are stored, the original data is re-structured from the read out subblocks, and the data is sent out as it is if no error is contained. When, if any subblock can not be read out normally because of damage of a recording area where the subblock is stored, the correct data is restored using other subblocks which are read out normally and error correction data and the restored data is sent out.
In the case of a disk array unit, even if one disk device is damaged completely, it is possible to restore the data by a procedure in which the damaged disk device is replaced with a new disk device and the data in other disk devices are used.
Some different types of disk array unit which involves error correction data have been known. Professor David A Patterson, UC Barclay School, classified the type into 5 classes, and proposed a new term namely level of RAID (Redundant Arrays of Inexpensive Disks). Summary of this proposal is described herein under.
RAID-1 is the class which doubles the data of a disk device, and alternatively called as mirrored disk. In a RAID-1, the quite same data are stored in two disk devices. In a RAID-2 or 3, the input data is divided in bit unit or byte unit, and divided data are stored in a plurality of disk devices. Hamming code is used in RAID-2, and parity is used in RAID-3 respectively as the error correction data. In a RAID-4 or RAID-5, the data is interleaved in sector unit. In a RAID-4, parity is stored in one disk device, on the other hand, in a RAID-5, parity is stored in a plurality of disk devices dispersedly.
RAID-3 and RAID-5 are used most popularly for the general disk array unit out of these RAID levels. FIG. 82 show an exemplary structure of a RAID-3 type disk array unit, and FIG. 83 shows an exemplary structure of a RAID-5 type disk array unit.
In the RAID-3 type disk array unit shown in FIG. 82, the input data is divided in byte unit, and the data divided in byte unit are stored in a plurality of disk devices. The parity is stored in a pre-determined disk device as the error correction data. Herein, parities P1-4 corresponding to the data having the number 1 to 4 stored in a plurality of disk devices and parities P5-8 corresponding to the data having the number 5 to 8 are stored.
In the RAID-5 type disk array unit shown in FIG. 83, the input data is divided in sector unit, these data are interleaved and stored in a plurality of disk devices dispersedly. In this case, data A, E, and I are stored in the first disk device, data B, F, and J are stored in the next disk device, data C, G, and parities PI-L corresponding to data I to L are stored in the next disk device. Data D, K, and parities PE-H corresponding to data E to H are stored in the next disk device, and parities PA-D corresponding to data A to D and data H and L are stored in the last disk device.
Recent development of computer system provides computers with the function to involve images and sound which are typical of multimedia data, a storage for these multimedia is some times referred as multimedia server. Because a large capacity and high transfer rate are required for a multimedia server, it is mostly realized in the form of disk array unit as a hardware system. An emphasis is placed on average processing performance for conventional computer server, on the other hand, an emphasis is placed on suppression of the worst value of the time required to complete processing for multimedia server.
For example, in the case of dynamic image, the motion is step-wise unless 30 images are displayed sequentially with a certain interval per second. The capacity of a disk device is insufficient for the motion, and if audio data becomes insufficient, then sound is interrupted and harsh noise is generated. Guaranty of upper limit time that processing is completed within the time at worst case is referred as guaranty of real-time. The guaranty of real-time is important for the multimedia server.
However, in the device explained above, video data and audio data cannot be processed quickly in real time and considerable time is required for editing even if the above device is used for the editing system, and so quick editing is impossible.
Moreover, when an audio signal is reproduced from the device explained above and a part thereof is updated in synchronism with the reproduced signal, it has been difficult to identify the buffering position of the recording signal and then match the position to the reproduced signal because the reproduced signal (old data) and recording signal (new data) are temporarily recorded respectively to independent buffers and the recording signal is delayed from the reproduced signal.
Moreover, the device explained above also has a problem that it is difficult to synthesize and record a plurality of reproduced signals in their arbitrary combinations.
Further, when video and audio signals are reproduced simultaneously at arbitrary positions on the above-mentioned device, a deviation of audio signal reproduction occurs due to the difference between the video frame frequency and the audio sampling frequency.